Superbugs are bacteria that have mutated to become resistant to common antibiotics which are no longer any use against them.
The most famous of the "superbugs" is methicillin resistant Staphylococcus aureus (MRSA), a common and usually harmless bacterium that is no longer knocked out by the antibiotic doctors would prefer to use.
Unlike MRSA, Clostridium difficile (C. difficile) it is a natural and normal part of the flora in the gut, and generally causes few health problems for the majority of the population.
It is however particularly tough and resilient.
When MRSA is detected through laboratory tests, doctors will use other antibiotics rather sparingly for fear that the bacteria will learn to evolve to resist those as well.
But if we blame over use of antibiotics for the rise of MRSA, it is also the culprit in the transformation of C. difficile from a harmless bug into a potential killer.
Healthy individuals will be able to keep C. difficile in check by the "good" bacteria in the gut, but because antibiotics do not discriminate, they kill off all the flora of the gut.
As C. difficile produces spores it is particularly good at survival.
The overuse of antibiotics for often minor infections, has caused some monster bugs to develop, while others, such as C.difficile, are given too much room to flourish and thereby cause harm.
According to the Health Protection Agency, about 3% of healthy adults and a third of babies have C. difficile in their bodies and most of the time they are fine.
It only becomes a problem for the frail, the elderly and those whose immune systems are damaged.
More often than not they have been on hefty courses of antibiotics.
The risk is increased by repeated enemas or gut surgery.
C. difficile when it is not kept in check, produces toxins that cause a watery diarrhoea, and severe diarrhoea is dangerous in very frail or elderly patients, as it is in babies, because it causes dehydration.
In some cases, C. difficile can cause severe inflammation of the bowel, which can be life-threatening.The very elderly can sometimes die.
People infected feel ill, but many of the symptoms are not easily distinguishable from other health problems, as they include fever, loss of appetite, nausea and abdominal pain.
Laboratory tests are needed to pinpoint C. difficile as the cause.
The bug can be treated and there are certain antibiotics which work, but the chances of a relapse are between 20% and 30% unless the gut is recolonised with healthy bacteria.